1. Field of the Invention
This invention relates to bearings in general, and in particular to a bearing assembly with yieldable spacer means for controlled deformation of a race with radial bearing load.
2. Description of the Prior Art
A rolling member bearing having concentric inner and outer races in an unloaded state will transfer nearly all of an applied radial load through the one or two rolling members which pass at any moment through the location about the radius through which the bearing load is transferred. This concentration of stress on only a few rolling members at this radial load location is caused by a combination of rolling member play and race deformation. It is a principal factor in wear and galling which affects bearing life.
Spreading the load, that is, applying a portion of the load through rolling members adjacent to those moving through the radial load location reduces the maximum load received by each rolling member. This extends bearing life and upgrades the maximum load support capability for a given bearing.
One arrangement for spreading the load in a bearing assembly in which the load is applied in an established direction defining a predetermined loading zone or radial load location, for example, as in a cam follower, is provided by U.S. Pat. No. 3,321,256 granted to M. Orain, May 23, 1967. It discloses using an elliptical trunnion, or spindle as the non-rotating inner race about which the rolling members and outer race rotate. The major axis of the ellipse is normal to the direction of the loading force.
The outer race is deformed inwardly at the location where it rides on the cam, forcing it to parallel the elliptical surface of the inner race over a small arc distance to either side of the radial load location. Rolling members within the area of deformation that centers on the radial load location are held in simultaneous intimate contact with the now paralleling inner and outer race portions, thereby sharing the load that would otherwise fall on one or two rolling members.
The elliptical shape of the trunnion is provided during manufacture. Alternatively, the shape is provided by machining it as a yielding hollow tube which deforms in response to load transferred back through the rolling members in the area of deformation.
Another arrangement for spreading the load over additional rollers is provided in U.S. Pat. No. 4,067,626 granted to McElwain on Jan. 10, 1978. For a bearing in a universal bearing joint, the bearing cup having an inner bearing surface, which serves as the outer race, is formed in an ellipse. The cylindrical outer surface of the trunnion serves as the inner race. In contrast with U.S. Pat. No. 3,321,256, it is disclosed that the major diameter of the ellipse is formed so that it coincides with the maximum loading point.
In an alternative arrangement, the inner surface of the bearing cup is cylindrical and a sleeve having elliptical inner surface and cylindrical outer surface is inserted between the rollers and the cylindrical inner surface of the bearing cup.
In another alternative arrangement, an insert having a cylindrical inner surface and elliptical outer surface which services as the inner race, is slipped on the cylindrical trunnion.